Control system for hydraulic presses



g 1940- R. w. DINZL 2.210.284

CONTROL SYSTEM FOR HYDRAULIC PRESSES Filed D56. 14, 19:5 3 ShGGtS-ShGSt1 Mar EZWZ' z 68 If] fiysv Q I ATTORNEYS Aug. 6, 1940. I R. w. DINZLCONTROL SYSTEM FOR HYDRAULIC PRESSES Filed Dec. 14, 193' I 3Sheets-Sheet 2 INVENTOR ATTORNEYS Aug. 6, 1940. R, w, DINZL 2.210.284

. CONTROL SYSTEM FOR HYDRAULIC PRESSES Filed D90. 14, 195' 3Sheets-Sheet 3 ATTORNEYS Patented Aug. 6, 1940 UNITED STATES ooN'rnoLsrs'rsm rnsssss w. Dinzl, Westfield, N. J., assignor to TheWatson-Stillman 00., Roselle, N. poration of New Jersey Richard FORHYDRAULIC J., a cor- Application December 14, 1937, Serial N... 179,767

8 Claims.

This invention relates'more particularly to improvements inpressapparatus of the type wherein a reciprocable press head is advancedon a working stroke by a hydraulically operated mechanism and, aftercompletion of thepressing operation, the press head is retractedautomatically by another hydraulically operated mechanism. Usually, insuch an apparatus, a complicated and costly pump of a variable delivery,or variable stroke; type has been required to supply the said advancingand retracting mechanismswith hydraulic pressure. An important object ofthe present invention is to provide, for such a press, a control systemdesigned for satisfactory employment of simple and inexpensive constantdelivery pump apparatus. Other objects of the invention will appearhereinafter.

In the drawings, Fig. l is a diagrammatic sectional View of the pressapparatus, with the reciprocable"press head in retracted position andthe control valve in neutral position;

Fig. 2 is a view similar to Fig. 1, with the control valve in a positionto cause advance-of the reciprocable press head and the latter advancedsufficiently to commence the pressing operation;

and

Fig.3 is a view similar to Figs. 1 and 2, with the reciprocable presshead advanced sufliciently to complete the pressing operation and thecontrol valve in a position to cause retraction of said press head.

My improved control system is shown inv connection with a press having afixed lower press head I and a reciprocable upper press head 2. The head2 has an upwardly extending ram 3 reciprocable in a fixed vertical,hydraulic cyllinder 4. A surge tank 5 is mounted upon the upper end ofsaid cylinder and communicates with the cylinder through a port 6. -Asurge valve I is provided to open and close said port. Hydraulicpush-back mechanism is provided to retract, or elevate, thepress head 2.This mechanism includes depending rams or plungers 8 borne by the head 2and reciprocable in fixed, vertical, hydraulic cylinders 9.

The surge valve 1 seats upwardly to close the port 6. It is constantlyspring-urged to closed position and has hydraulically operated means toshift it to open position. A bracket ,lll is mounted within the surgetank and bears a fixed, vertical, hydraulic cylinder II. The valve has avertical stem I2 forming a ram or plunger whose upper end portion isreciprocable within the cylinder II. The valve stem bears a frame oryoke which comprises a horizontal cross bar I3 aflixed to the stem at apoint between the valve and the lower. end of cylinder ll, anotherparallel cross bar located above the cylinder H, and vertical tie-rodsl5 rigidly connecting said cross bars. A spring is interposed betweenthe closed upper end of cylinder H and the upper cross bar It constantlyurges the frame upwardly to close the valve. As will be explainedherein- 5 "er, cylinder I l is supplied with hydraulic pressure to forcethe plunger l2 downward to open the valve.

A constant delivery main pump ll supplies the advancing and retractingmechanisms for the press head 2 with hydraulic pressure'to operate them.This pump is shown diagrammatically. It may be of a simple conventionaltype. It is located directly over an open supply tank l8 and has areceiving connection l9 with the lat-" ter. A main delivery pipe 2!]leads from the pump outlet to a control valve device which in turn hasdelivery connections with the press head advancing mechanism, the presshead retracting mechanism and the surge tank. These connections will bedescribed hereinafter. There is a check valve 20 in the pipe 20 andopening toward the valve-device. There is also a fluid return connectionbetween the surge tank 5 and the pump supply tank It. 'I'his'returnconnection is a constantly open overflow pipe 2! leading from themaximum permissible fluid level of the surge tank to the pump supplytank. The fluid employed in thesystem is preferably oil.

The control valve device comprises a cylindrical valve casing 22 closedat both ends and containing a reciprocable valve 23 i The valve casing22 has a port 24 located at a mid point in its length, ports 25 and 26spaced outwardly from opposite sides of port 24, and ports 21 and 28located near the opposite ends of the casing. The port 25 has branches25 and 25 opening into the valve casing at points slightly spaced alongthe casing. The valve is of a plunger type and it has spaced heads 29and 30 fitted within the casing and connected by a reduced portion orneck. Stems 3| extend from opposite ends of the valve, through aperturesin the ends of the casing, and each stem bears a solenoid core 32, oneshiftable through a solenoid winding 33 and theother through a solenoidwinding 34. By energiz'ation, of these windings in sequence the valve isshifted to cause advance and retraction of the press head 2. Whenneither solenoid is energized the valve is held in a neutral position bytwo opposed coiled springs 35 and 36. These are enclosed by a housing 31mounted upon one end of the valve casing and they encircle one of thevalve stems and bear against opposite sides of an abutment disk 38affixed to the stem.

The main delivery pipe 20 leads from the pump I! to the valve port- 24.A delivery pipe 39 leads from port 25 to the cylinder 4 of the presshead advancing mechanism. A pipe 40 leads from port 26 and is connectedto the lower ends of the push-back cylinders 9. This pipe 40 has a checkvalve 4| opening toward the push-back cylinders. Provision is made forrestricted back flow past said check valve. There is shown a smallbypass pipe 42 around the check valve. The check valve may instead havea small port to permit back flow. A pipe 43 leads from both of the ports21 and 28 to the surge tank 5. The pipe 39 which leads to the cylinder 4has a branch 44 opening into a small cylinder 45in which there is fitteda plunger 46 which is shifted by a predetermined pressure in pipe 39against the resistance of'a compression spring 41. Said plunger has aprojecting stem bearing an electric switch member 48 whose purpose willbe explained hereinafter.

There is provided an auxiliary hydraulic connection between the surgetank and the push back cylinders 9 to compensate for leakage from thecylinders. This connection is independent of the controlvalve device. Itcomprises a pipe 49 leading from the surge tank, a pipe 50 connected tothe pipe 49, and a long pipe 5| connected at an intermediate point topipe 50. One end of pipe 5| is connected to pipe 40 which leads to thepush-back cylinders. The opposite end of the pipe 5| is connected to thesmall cylinder ll forming part of the mechanism for opening the surgevalve. livery auxiliary pump 52 is connected into the pipe 49 to causeforced flow from the surge tank and through the said connected piping.Pipe 49 has a relief valve 53 to limit pressure therein and pipe 50 hasa check valve 54 opening toward pipe 5|. The pump 52 and the piping4950-5l are of materially less capacity than the main pump I1 and thepiping leading to and from the control valve device.

There is a relief connection between the pushback cylinders 9 and thesurge tank to limit the pressure developed in said cylinders by theauxiliary pump 52. Said relief connection comprises a pipe 55 forming anextension of the pipe 40. A valve device 56 is connected into pipe, 55to control flow therethrough. Normally said valve device is closed butit is opened in response to a-predetermined extent of retraction of thereciprocable press head 2. The valve device comprises a casing 51 and aslide valve 58 mounted in the casing. A spring 59 within the.

casing constantly urges the valve to closed position. The valve has astem 60 projecting from the casing and, engageableby a small lever 6|mounted to rock about a fixed axis. The lever has one arm engageablewith the valve stem and another arm bearing a roller 62. A slide- 63 ismounted to shift vertically and has a cam surface 64 engageable withsaid roller when the slide is. shifted upwardly to rock the lever anddepress the valve to open position against the resistance of the spring59. The slide 63 bears a depending stem 65 upon which a collar 66 isadiustably secured. The collar forms an abutment engageable by a thrustmember 61 aflixed to the reciprocable press head. The collar is adjustedalong the stem 65 to such position that it A small constant dewill beengaged by the thrust member 61'to shift the slide 63 upwardly and causethe valve 58 to be shifted to open position when the press head 2 hasbeen elevated to a predetermined height.

Electrical circuits and switches are provided to control energization ofthe solenoids 33 and '34 and thereby, through the control valve device,control the advance and retraction of the reciprocable press head 2. Theswitches include a push button switch .68 operable to cause advance ofthe press head, the switch 48 which is operated automatically to causeretraction of the press head at the completion of a pressing operation,a push button switch 69 operable to arrest advance of the press head,and a push button switch 10 operable to cause retraction of the presshead before it has completed a working stroke. There is also a switch Hoperable in response to retraction of the presshead to a predeterminedheight to cause shiftingpf the control valve to neutral position. Theswitch H is constantly urged to circuit-closing position by a spring 12and has a stem 13 engageable by a small lever 14, similar to the lever6| for operating the relief valve 58. Said lever 14 is mounted forrocking about a fixed axis and has an arm engageable with the switchstem and an arm bearing a roller 15. The latter is engageable by a camsurface 16 on the slide 63 to rock the lever and open the switch II whenthe slide is shifted upwardly by engagement of the thrust member in thesurge tank it overflows into the pipe 2! and is returned to the pumpsupply tank 18. This circuit is a very desirable feature of the system.While the press is idle the constantly driven pump maintains a desireddepth of fluid in the surge tank regardless of pump leakage or loss ofeificiency. It prevents accumulation of fluid in the supply tank due topump leakage and thus avoids the necessity for draining ofi' excessfluid from said tank.

When the control valve is in neutral position there is also an opendelivery connection from the main pump to the pipe 39 leading to thepress cylinder 4. This connection, however, is purely an incidental oneas the surge valve is open and fluid delivered through the pipe 39 canflow up into the surge tank. Flow from" the main pump to the push-backcylinders, through the pipe 40, is blocked by the head 30 of the controlvalve, and the push-back cylinders are supplied with hydraulic pressureby the auxiliary pump 52 which delivers from the surge tank through thepiping 49, 50 and 5|. The auxiliary pump is constantly driven and itsdelivery compensates for leakage from the push-back cylinders andprevents settling of the press head 2. The pressure maintained in thepushback cylinders is also maintained in thesmall surge valve cylinderH, through the connection of pipe 5| with said cylinder. This pressurein cylinder ll holds the surge valve 1 open against the resistance ofthe spring l6. Should the pressure in the push-back cylinders 9 exceedthat required for sustaining the press head 2 and force the latterupwardly, as shown in Fig. 1, the slide 63 will be shifted upwardly torock-'the small lever'6l and depress the valve 58 to .open positionagainst resistance of the spring 59. That will permit escape of fluidfrom the pushback cylinders through the pipe to the surge tank and limitupward movement of the "press head.

The press head 2 is caused to start downwardly on a working stroke bypressing the push button switch 68. This momentarily closes an electriccircuit including a line wire L, a conductor 11, the push button switch89, which is normally in closed position, a conductor 18, a conductor19, a relay armature 89, a conductor 8!, a conductor 82, a conductor 83,a relay winding 84, a conductor 85 and a line wire L. By the currentthrough the relay winding the armature 89 is shifted to close the relayand close a circuit including line wire L, conductors I1, 18 and I9,armature 80, a conductor 86, a conductor 81, the valve-operatingsolenoid 33, a conductor 88 and the line wire L". At the same time thereis closed a circuit including said conductor 86, switch 48,

conductor 83, relay winding 84, conductor 85 and line wire L, to holdthe relay closed' andthus maintain the circuit through the solenoid 33after release of the push button 68. Energization of solenoid 33 shiftsthe control valve 23 upwardly, against the resistance of spring 35, topress head advancing position as shown in Fig. 2.

When the control valve 23 is in the position shown in Fig. 2 the maindelivery pipe 20 is connected, through port 25 to pipe 39 leading topress cylinder 4 which is still in communication with the surge tank, asclosing'of'the surge valve 6 is delayed. The push-back cylinders 9 arenow in delivery connection with the surge tank through the pipe 49, theby-pass 42 around the check valve 4|, the valve casing 22 and the pipe43. Consequent relief of pressure in the pushback cylinders permits thepress head 2 to settle by gravity. The pressure upon the fluid in thepush-back cylinders as the plungers 8 move downward is transmittedthrough the pipe 5| to the small surge valve cylinder II and serves tohold the surge -Valve open. When, however, descent of the press head isarrested by contact of a die D, borne said head, with the work W, thepressure of the plungers 8 upon the fluid in the pushback cylinders andthe pipe 5| and the small cylinder ll ceases and the spring l8 closesthe surge valve. The latter is held closed by main pump pressurereceived in the press cylinder through pipes 29 and 39 and the presshead 2 is positively forced downwardly by said pressure, to perform thepressing operation.

Upon completion of the pressing operation increased pressure in thepress cylinder 4 and in pipe 39 overcomes the resistance of spring 41and shifts the small plunger 46 and the switch 48 to break theelectrical connection between conductors 83 and 86. Since the relay -84is dependent upon said connection, when the connection is broken therelay opens and thereby opens the circuit including the solenoid 33. Thesaid ,shift of the pressure responsive switch 48 also causes it toconnect two conductors 89 and 99, as shown in Fig. 3. Thereby there isclosed a circuit including line wire L; conductors I1, 18 and 19, thearmature 9| of another relay, conductor '89, switch 48, conductor 99, arelay winding 92,

a conductor 93 and the line wire L. Thereby the relay 9l-92 is closedand a circuit is estab-'- lished through condu ctors 11, I8, I9,armature 9|,

a conductor 94, a conductor 95, the solenoid 34, a conductor 95 and theline L. Consequent energization of solenoid 34 causes the control valve23 .to be shifted downwardly, against the resistance of spring 36,-to-press head retracting position, as shown in Fig. 3. When the relay.9l-92 closes it also closes a circuit including a conductor 91connected to the conductor 94 in the circuit just described, the switchII, a conductor 98 and the conductor 99 leading to the relay winding 92.Thereby the relay 9l92 is held closed so long as the switch H remainsclosed, and said relay holds closed the circuit including the'solenoid34.

When the control valve 23 is in the position shown in Fig. 3communication between the delivery pipe 20 and the pipe 39 leading tothe press cylinder 4 is blocked by the valve head 29. Valve head 39 isin a position to open communication between the pipe 28 and the pipe 40thus connecting the main pump to the push-back cylinders :9. Theconsequent pressure in the pipe 40 and in the push-back cylinders istransmitted through the pipe 5| to the small surge valve cylinder II p Ytoopen the surge valve and place the cylinder 4 in communication withthe surgetank. The pres- -sure in the push-back cylinders then raisesthe press head 2 until the thrust member 61 home by the head engages thecollar 66 on stem of the slide 53 and forces the slide upwardly. Theupward shift of the slide rocks the small lever 14 to shift the switch Hto open the circuit through the relay winding 92. The relay 9l-'-92 thenopens and thereby breaks the circuit including the solenoid 34. Spring38 then restores the control valve 23 to neutral position.

Advance of the press head 2 may be arrested, when necessary, before theworking stroke is completed by pressing the normally closed push buttonswitch 89. Thereby connection between the conductors l1 and I8 isbroken, permitting the relay 80-84 to open and break the circuit throughthe solenoid 33. Valve spring 35 can then restore the control valve 23to neutral position. Operation of the push button switch 'lfl enablesthe press head to be retracted independently of the pressure responsiveswitch 48. Switch 19 is normally open andwhen it is pressed it connectsthe conductors 89 and and completes the circuit previously described forclosing the relay 9I--92. Closure of said relay completes the circuitpreviously described for energizing the solenoid 34. The control valve23 is thereby shifted downwardly to cause retraction of the press head.f

What I claim is: a 1. In a press apparatus having press head advancingmechanism and press head retracting 'mechanism, both operable byhydraulic pressure, a surge tank, and a surge valve to controlcommunication between the surge tank and said ada I eluding a constantdelivery auxiliary pump of low capacity in comparisonfwith the main pumpto deliver fluid from the surge tank to the retracting mechanism tocompensate for leakage from the latter, means responsive to apredetermined ex-- tent of press head retraction to vent the retractingmechanism to the surge tank to limit retraction, and means operable inresponse to a predetermined fluid pressure in the retracting mechanismto open the surge valve.

2. In a press apparatus having press head advancing mechanism and presshead retracting mechanism, both operable by hydraulic pressure, and asurge tank in valved connection with said advancing mechanism,- acontrol system for said mechanisms comprising a constant delivery mainpump, a hydraulic supply tank for said pump, the pump having a receivingconnection with said tank and delivery connections with said advancingand retracting mechanisms and with the surge tank, valve means operableto control flow through said delivery connections for alternateoperation of said advancing and retracting mechanisms and operable todirect the main pump delivery to the surge tank to render the pressidle, a hydraulic return delivery connection leading from the surge tankto said pump supply tank for gravity flow of excess fluid from the surgetank, a hydraulic delivery connection between the surge tank and theretracting mechanism independent of said valve means and including aconstant delivery auxiliary pump to compensate for'leakage from theretracting mechanism, a hydraulic relief connection between theretracting mechanism and the surge tank and also independent of saidvalve means to relieve pressure in the retracting mechanism, and valvemeans normally closingsaid re lief connection and operable in responseto a predetermined extent of press head retraction to open the reliefconnection to limit retraction.

3. In a press apparatus having press head advancing mechanism and presshead retracting mechanism, both operable by hydraulic pressure, a surgetank, and a surge valve to control communication between the surge tankand said ad- .vancing mechanism and constantly urged to closed position,a control system for said mechanisms and surge valve comprising aconstant delivery pump having delivery connections with said mechanismsand with the surge tank, valve means operable to direct delivery fromthe main pump to said mechanisms and to cause flow from the latter tothe surge tank, for alternate operation of said mechanisms and operablealso to direct said delivery to the surge tank to render the press idle,fluid return means independent of said valve means to deliver excessfluid from the surge tank to the main pump, means operable in responseto a predetermined pressure in the advancing mechanism to causeoperation of said valve means for press head retraction, forced feedmeans independent of said valve means and said pump to delivery fluidfrom the surge tank to the retracting mechanism to compensate forleakage from s the latter, means responsive to a predetermined extent ofpress head retraction to vent' the retracting mechanism to the surgetank to limit retraction, and means operable in response to apredetermined fluid pressure in the retracting mechanism to open thesurge valve.

4. In a press apparatus including press head advancing mechanism andpress head retracting mechanism, both operable by hydraulic pressure, acontrol system for said mechanisms comprising a constant delivery mainpump having delivery connections with said mechanisms, fluid returnmeans to .conductsfluid discharged .from the pump back to the pumpinlet, control valve means operable to control delivery from the pump tosaid mechanisms and to cause flow from the latter to said fluid returnmeans, for press head reciprocation, and operable also to fully by-passthe pump delivery to said fluid return means, a hydraulic deliveryconnection between said fluid return means and said retracting mechanismindependent of said main pump and said valve means and including aconstant delivery auxiliary pump of low capacity compared with said mainpump, to compensate for leakage from the retract ing mechanism, ahydraulic relief connection between the retracting mechanism and thefluid return means and also independent of said valve means, and valvemeans for closing said relief connection and responsive to apredetermined extent of press head retraction to open the connection tolimit retraction.

5. In a hydraulic press apparatus including press head advancingmechanism and press head retracting mechanism, both operable byhydraulic pressure, a surge tank associated with said advancingmechanism, a surge valve to control flow between said tank and theadvancing mechanism, hydraulically operable means for opening the surgevalve, a constant delivery main pump in receiving connection with thesurge tank, valve means operable to control delivery from said pump tosaid mechanisms and exhaust from said mechanisms, for press headreciprocation and operable also to fully to render the press idle, aconstantly open hydraulic connection between said retractingmechanismand said-surge valve opening meansja con-' stant deliveryauxiliary hydraulic pump of lowcapacity in comparison with the main pumpin receiving connection with the surge tank and having a check-valveddelivery connection with said hydraulic connection between the surgevalve opening means and the retracting mechanism to supply the latterwith hydraulic pressure independently of the main pump to compensate forleakage, a hydraulic relief connection between the retracting mechanismand the surge tank, and valve means for closing said relief connectionand responsive to a predetermined extent of press head retraction toopen said relief connection to limit retraction.

6. In a hydraulic press apparatus including press head advancingmechanism and press head retracting mechanism, both operable byhydraulic pressure, a surge tank associatedwith said advancingmechanism, a surge valve to control flow between said tank and theadvancing mechanism, hydraulically operable means for opening the surgevalve, a main pump in receiving connec-. tion with the surge tank, valvemeans operable to control delivery from said pump to said mechanisms andexhaust from said mechanisms, for press head reciprocation, a constantlyopen hydraulic connection between said retracting mechanism and saidsurge valve opening means, an auxiliary hydraulic pump of low capacityin comparison with the main pump in receiving connection with the surgetank and having a delivery connection with said hydraulic connectionbetweenthe surge valve opening means and the retracting means to supplythe latter with hydraulic pressure independently of the main pump tocompensate for leakage, a hydraulic relief connection. between theretracting mechanism and the surge tank, and valve means for closingsaid relief connection and responsive to a predetermined extent of presshead retraction to open said relief connection to limit retraction.

7. In a press apparatus including press headby-pass the pump delivery amain pump having delivery connections with said mechanisms, fluid returnmeans to conduct fluiddischarged from the pump back to the pump inlet, asingle control valve operable to control delivery from said pump to saidmechanisms and to cause flow from the latter, for press headreciprocation, and operable also to a position to cut oil delivery fromsaid pump to said retracting mechanism after press head retraction andat the same time fully by-pass the pump delivery to said fluid returnmeans, a constant vdelivery auxiliary pump of low capacity in comparisonwith said main pump and having a delivery connection with saidretracting mechanism to supply the latter with hydraulic pressure tocompensate for leakage therefrom .while the main pump is bypassed andcut off from the retracting mechanism, by-pass means for said auxiliarypump including valve means responsive to a predetermined extent of presshead retraction by the aux- .iliary pump to direct the discharge of thelatter back to the inlet of the auxiliary pump, an electromagneticdevice mechanically connected to the said control valve and operable toshift the latter to a position for press head advance, anotherelectromagnetic device mechanically connected to the control valve andoperable to shift it to a position for press head retraction, and meansresponsive to deenergization of both of said electromagnetic devices toshift the control valve to its said cut-off and by-passing position.

8. In a press apparatus including press headadvancing mechanism andpress head-retracting mechanism, both operable by hydraulic pressure, acontrol system for said mechanisms comprising a main hydraulic pumphaving delivery connections with said mechanisms, fluid return means oconduct fluid discharged by the pump back to the pump inlet, a singlecontrol valve operable to direct delivery from the pump to saidmechanisms and to cause flow fromthe latter to the fluid return means,for press head reciprocation, and operable also to by-pass the pumpdischarge to said fluid return means, fluid pressure-operated meanshaving a hydraulic connection with said advancing mechanism tocausepress head retraction in response to a predetermined hydraulicpressure in the advancing mechanism, a switch operable in response to apredetermined degree of press head retraction to stop the retractingmovement through the control valve, a constant delivery auxiliary pumpof low capacity in comparison with said main pump and having a deliveryconnection with said retracting mechanism to supply the latter withhydraulic pressure to compensate for leakage therefrom while the mainpump is by-passed and cut off from the retracting mechanism, and by-passmeans for said auxiliary pump including valve means responsive to anadditional predetermined degree of press head retraction by theauxiliary pump to direct the discharge of the latter back to the inletof the auxiliary pump.

RICHARD W. 'DINZL.

